This invention relates to methods of diagnosing and compensating for malfunctions of a spray header. In a particular sense, the invention is directed to methods of detecting and correcting such malfunctions in rolling mill spray cooling systems.
Mills for rolling metal sheet (strip) commonly employ spray headers for cooling roll and/or strip surfaces with sprays of liquid coolant. As contemplated herein, a spray header is a device having a manifold and a plurality of nozzles each including (and controlled by its own valve, the nozzles being arranged side by side to discharge, in parallel, sprays of a liquid supplied to the manifold. A rolling mill spray header is typically operated to distribute sprayed liquid coolant substantially uniformly across the surface of a roll or strip, although controlled nonuniform distribution may be provided for particular purposes. It is known to control the nozzle valves, for example by a suitable computer, in response to sensed variations in pertinent temperature conditions.
Difficulty has heretofore been encountered in detecting and correcting spray header malfunctions such as total or partial clogging of a nozzle or failure of its valve (reference herein to valve failure will be understood to include failure of the valve itself and/or of any actuator means or mechanism associated therewith). When valve or nozzle malfunction occurs, delivery, of spray through the affected nozzle is impaired or interrupted, and the roll or strip surface portion sprayed by that nozzle receives inadequate or excessive coolant, with potentially deleterious consequences. In a rolling mill, it is frequently not feasible to ascertain individual nozzle valve malfunctions by direct visual inspection, and diagnostic as well as corrective procedures have necessitated time-consuming shutdown of the mill.